Edge gap as a geometric parameter to characterize the sealing performance of compressor valves

Leakages in valves can significantly affect both the isentropic and volumetric efficiencies of small reciprocating compressors used in household refrigeration systems. This paper reports an analysis of leakage in valves of low-capacity reciprocating compressors. An experimental setup based on the constant volume method is developed to measure leakage in suction and discharge compressor valves independently. The valve leakage is measured for three different valve designs and the concept of edge gap is proposed as a useful parameter to characterize the sealing performance of such valves and to predict the resulting leakage of different refrigerants. This parameter is affected by the characteristics of the reed and valve seat surfaces and the pressure load acting on the valve. The edge gap is determined through a combined experimental-numerical procedure by matching leakage predictions obtained from a validated numerical model with the corresponding measured values. The results indicate that leakage can vary considerably with valve design, with typical edge gap values being between 0.11 and 0.61 µm.